Snowflake said:
Only forms which pose an issue to NFUs are those which require the Force
A lot of people have asked about which forms a droid could use. NFUs can use the same ones. Shii-Cho, Makashi, Djem So, and some aspects of Niman are all things that NFUs should be able to use just fine.
Soresu requires the Force for precognition. In particular, attempting blaster bolt deflection is basically suicide without being able to see the future.
Ataru requires a constant and deep connection to the Force to assist in impossible acrobatics.
Niman heavily relies on practical application of the Force, but there's nothing saying that you can't pursue it for bladework alone. You'll be using a gimped and incomplete version of the form, but it's still functional.
Juyo, much like Ataru, requires a constant and deep connection to the Force, both for physical feats like acrobatics and endurance, and for the primal connection to the battle from which Juyo draws its energy.
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So if your NFU gains the ability to use a lightsaber through RP, I'd suggest sticking to Forms I, II, V, and maybe VI. They're the most NFU-friendly, as their techniques don't rely on the ability to manipulate causality with your mind.